Rheostat.



5. a. VBZTER. RHEUSTAT.

APPLICATION FILED HOV. 19, 1902.

N0 MODEL.

PATENTED OCT. 6, 190

its, as desk! l e-tented Getober 6, 1903.

PATENT Fr -16E,

JOSEPH G. VETGFER, OF ASTORlA, NEW YORK.

RHEQSTAT.

$EEGIFIGAEIQN forroing part of Letters Iatent No. 740,787, dat d O tobe 8, 19,03. Application flea November 19,1902 Serleillo. 131,989. (llnmodel) .To @4 6 whom it may concern: i

Be it known that I, Jose-re: O. VETTER, a citizen of the United States, and a resident of Astoria, tate ofllew York, have invent ecl certain new and useful Improvements in Plheostats, of ivhich the following is a specification, accompanied by drawings.

lily intrezition relates to rheostats curl to e resistance thereof-5 and its objects are to improve upon the construction of rheostats in general," although my apparatus is intecrlcd more especially for controlling circuits of low amperage, such as used in meclical work. The apparatus may, however, be used in any connection towhich it may be adapteti.

Other objects of my invention are to enable very small-variations in current to be obtained with great accuracy and secure efi ciency and durability with simplicity of ports. Further objects of my invention will hereinafter appear; and to these ends my invez1 tiou consists of apparatus for carrying out the above objects embodying the features of construction, combination of elements, and arrangement ofparts, substantially as hereinafter fully described in this specification and shown in the accompcuyihgdrawiogs, in

which i j Figural is a vertical transverse sectional View 05 a rheostat embodying" my invention, end if is a perspective View of one of the electrodes. l i Referring to the drawings, A represents a base of suitable insulating material upon which the apparatus is arranged. The princlple upon which the rheostateperates is that oil a cosngjressible and expausible conrluctofi' the conductivity and resistance of which are varied by a. varying pressure thereon. While this eomcressible and expansible comluctor he formed in various ways, in this instance I have shown it consisting of a mass of elastic and relatively inelastic particles which may be compressecl or squeezed into dense are compact form, thereby decreasing the resist. hce of the maes'wlthin certain lllll- According to the construction shown one electrode B is secured to the base A ill-{lily suitable manner, as by means of the screw 0, while another electrode D is adapted to be moved toaud from the electrode l5, and the mass of conrluctin g material is arranged between the two electrodes and preferably coufinc latz-irally, as by means of the receptacle E, which, as shown, is of insulating materialas, for instance, hard rubber. V v

The mass of material forming the resistance consists of any suitable granulated or powdared elastic material, such as soft rubber, as

shown, the larger particles G representing particles of such elastic material, while the liner particles Hero of material which is rela- "vcly inelastic compared with the particles G, such as granulated or powdered carbon or auyother suitable conductor or semicom doctor. The'partlcles of material G anclHare in this instance mixed together dry, although I am not to be understood as limiting myself to clry mixture nor to a mechanical mixture only.

Any suitable proportion may be obtained between the elastic and relatively inelastic granulated that they be mixed in such proportions that the greatest conductivity isobtained under pressure, it being-desirable that the minimum amount of the elastic material, such as rubber, be used to impart to the mass sufficient elasticity to obtain very small variations in conluctivity under pressure.

As the upper electrode D is pressed down.

upon the mass of particles between the electrodes it Will be seen that the particles of conducting material will be pressed closer tomaterial, it only being necessary gcther into more intimate contact with each other,'thus lessening the air-gaps between the particles end increasing the conductivity of the mass. The particles G of elastic material are also squeezed together, audit not 'of compressible material themselves their the conformation will be changell without substantial diminution in size, so that as the pressure on the mass is gradually released the elastic particles G will tend to spring back into their original form, thus disturbing the liner particles H and tending to expend the mass and force the electrode D away from the electrode 13'. In other words,

shape and the elastic particles G- tend to restore the ina-v terial after compression toits loosened form curl at the same time force the upper elecmet I) away from the electrode B. When the uiatcrial is heiu'g compressefi, the parti- This gradual compression of the carbon par.

ticles makes possible very small verietions in the conductivity of the material end thus permits small variations in the current to be obtained.

.It will be seen that the upper end lower electrodes of the appnrntus are dished or hollowed on the inside and each provided with inwardly-projecting portions I, adapted to be brought into contact when desired and complete the metallic circuit from one electrode to the other. It has been found that it is not necessary that the inwardlyprojecting points I of the electrodes be brought into actual contact to get the maximum current.

.By forming the electrodes as shown, dished or hollowed, it will be seen that the particles are not only compressed in a verticalv direction, but at angles to the vertical in directions normal to the curvsture'of the surfaces of the electrodes, so that the particles are squeezed together form.

Any suitable means may be provided for pressing the electrode D toward the electrode B, as shown in this instance a screWJ being supported in the frame K and adapted to be screwed down upon the electrode D by means of e milledjiand-wheel L, preferably of insulating material, asv shown. In this instance a, spring 0 is shown for insuring the rnovemerit ot the electrode D away from the electrode B when the pressure on the said les named electrode is gradually decreased. The spring 0, as shown in this instance, surrounds the receptacle E and bears against the base or plate A and against e Henge Pen the electrode D, so that when the sold electrode is pressed down Ward the spring 0 is com pressed,

tending to raise the electrode when the pres sure is gradually removed.

Any suitable electrode connections mzty he made which will include the granular resistsecs as a part of the circuit, as shown one binding-screw Q being connected by means i of n wire R, with the frame K, while another bindin -scr W S is connected b nieces of s c 3 into compact and dense wire T, with the central screw C, which holds the electrode l3 upon. the lasso-piste A, circuit thus being completed with the apparatus from tively inelastic granular particles confined from expanding laterally between said, else trodes and. forming a conductor, and means for varying the pressure upon said mass of particles to very its resistance, substantially as set forth.

2. An electric resistance consisting ofs. mess of elesticgraunler perticlesend reletivelyinelastic granular particles,suhstcntisllyes set forth.

3. An electric resistance consisting ofn mass of elastic non-conducting granular particles and relatively inelastic conducting granular particles, substantially as set forth.

4, Arheostnt comprising a base, two electrodes one of'which is connected to the base, a. spring tending; to force the other electrode away from the base, adjustable means for re sisting theection of sold spring and a mass of granular-compressible and ex nnsible conducting materiel confined laterally between said electrodes, substantially as set forth.

5. A rheostst comprising an inelastic receptacle, cup shsped electrodes in the same having centrally-arranged and inwardly-projecting portions adapted to be moved into contact with each other, a compressible and enpnnsible grsnulsted or powdered conductor between said electrodes, and menus for vary ing the pressure upon the said conductor to very its resistance.

In testimony whereof I name to this specification in the presence of two subscribing Witnesses.

JOSEPH C. VETTER. Witnesses:

H. G. Oconng'ilix, E. VAN ZANDT.

have signed any 

